Key technologies for long-period high and stable production of the Puguang high-sulfur gas field, Sichuan Basin

Puguang Gas Field is a high-sulfur gas field with the greatest proved reserves in China, and its reservoirs are dominantly of reef shoal facies with the characteristics of strong heterogeneity, strong edge water energy and high sulfur content, which brings a series of technical difficulties and challenges to its development, such as poor seismic prediction accuracy, fast edge water advancement, rapid productivity decline, gradual sulfur deposition precipitation, and poor gas well productivity and reservoir production effect. To deal with the difficulties and challenges in the development of Puguang Gas Field, this paper summarizes the technological researches and field practices that have been carried out since the '13th Five-Year Plan' to achieve long-period high and stable production in Puguang high-sulfur gas field. And the following research results are obtained. First, the rock physics template for the prediction of intra-platform shoal reservoir is established, the countermeasures for effective production are proposed, and the acid fracturing process of "self diverting clean acid + resistance reducing slickwater + temporary plugging in fractures" to create complex fractures is developed, so that the ultra-deep low-grade intra-platform shoal reservoirs of reef shoal facies can be produced effectively. Second, the kinematic equation of gas and water front of reef shoal facies reservoir is established, new sulfur resistant ternary compound foam drainage agent and bridge plug with high sulfur resistance and ultra-high expansion ratio are developed, and the through-tubing plunger water plugging technology is developed to achieve water production control and gas production stabilization throughout the life cycle of high-sulfur gas well. Third, the precipitation mechanism of elemental sulfur from high-sulfur natural gas is revealed, a sulfur deposition distribution model of high-sulfur gas reservoir is established, rapid dispersive sulfur solvent is developed, and a jet flushing process is supported to form the wellbore sulfur deposition treatment technology. In conclusion, in Puguang Gas Field, the current edge water fingering leads to a very complex distribution of remaining gas, sulfur deposition gradually expands from the wellbore to the formation, and the wellhead pressure is close to the output pressure. In the next step, therefore, it is necessary to carry out technical researches such as fine characterization and potential tapping of remaining gas, precise water plugging, reservoir sulfur deposition treatment, and pressurized production of gathering and transmission system, to further improve its gas field development effect and recovery factor. © 2023 Natural Gas Industry Journal Agency. All rights reserved.